Activated carbon is a carbon material with a developed pore structure. It is widely applied to the fields of medicines, environmental protection, food, electrons, chemical industries, agricultures, national defense and the like, particularly applied to aspects such as gas storage, catalyst carriers and sewage treatment, due to its characteristics of large specific surface area, rich surface functional groups, high adsorption capacity and the like.
Because a biomass pyrolysis technology is a technology for turning wastes into treasures, this technology is a hotspot studied by many scholars and can prepare activated carbon, bio-oil, combustible gas and the like. Biomass pyrolysis generally includes slow pyrolysis and fast pyrolysis. The slow pyrolysis generally aims to prepare the activated carbon, and the fast pyrolysis aims to prepare the bio-oil. A heating rate of the slow pyrolysis is generally less than 0.1-1° C. per second, and a heating rate of the fast pyrolysis is generally more than 100-200° C. per second. The slow pyrolysis generally takes relatively long time, and even several days sometimes, to prepare the activated carbon.
Fluidization technologies, particularly a fluidized bed technology, a spouted bed technology and a circulating fluidized bed technology, are more and more widely applied to the field of biomass pyrolysis. Fluidization of biomass in a pyrolysis process not only increases the pyrolysis or activation efficiency of material, but also facilitates feeding and discharging of the material, thereby guaranteeing graininess of the material.
Preparation of the activated carbon includes two methods, namely a physical activation method and a chemical activation method. The physical activation method includes a carbonization step and an activation step. Carbonization temperature is low, and activation temperature is high and is generally 800-1000° C. The physical activation method has the characteristics of simple operation, environmental friendliness and no pollution, but has the disadvantages of long operation time, high activation temperature and low activated carbon quality. Activation gas generally includes CO2 and water vapor. The chemical activation method includes soaking a chemical reagent and the material and activating the mixture at a high temperature, but the activation temperature is low, which is generally 350-600° C. The chemical activation method has the characteristics of complicated operation and severe pollution, but has short operation time, low activation temperature and high activated carbon quality. Common activation reagents include KOH, H3PO4, ZnCl2 and the like.
Patent 201510383207.6 describes a method for preparing activated carbon. In this method, the carbonization temperature is 500-650° C., the activation time is 40-120 min, and the heating rate is 3-10° C./min.
Patent 201110021089.6 describes a method for preparing activated carbon from biomass wastes. In this method, the carbonization temperature is 400-600° C., and the activation time is 0.5-1.5 min.
Patent 201110193274.3 describes a method for preparing cocoanut activated carbon. Raw materials are carbonized in a flat-bottom carbonization furnace at 900° C. for 5 hours at first, and then are activated at 700° C. for 2 hours.
By checking other patents or documents for preparing the activated carbon, it can be known that in the process of preparing the activated carbon, many researchers select a static reactor without considering the fluidization of the material, but the fluidization of the material can guarantee the graininess of the material, facilitate the discharging of the material and reduce subsequent operation such as crushing of the activated carbon. Then, the activation time is too long, the material heating rate is low, and the operation period is basically 0.5-2 hours, and even longer.
The present disclosure provides a novel method for preparing high specific surface area activated carbon through rapid activation under fluidization. The material in this method is in a fluidized state, so that the method guarantees the graininess of the material and greatly facilitates the feeding and discharging of the material. In addition, the method is extremely short in activation time. In a pyrolysis reactor of the same size, the treatment capacity may be greatly increased, which has a profound effect on industrialization.